This invention relates generally to cutting accessories used with powered surgical handpieces to perform endoscopic surgical procedures. More particularly, this invention relates to elongated cutting accessories that are especially useful for performing surgical procedures at difficult to reach surgical sites such as the forward facing, anterior region, of the spine.
Today, it is common that when a surgical procedure needs to be performed at a surgical site within the body of a living being that the procedure be performed endoscopically. In an endoscopic surgical procedure, an endoscope is placed in the surgical subject and positioned at the site at which it is necessary to perform the procedure. Other surgical instruments are also positioned at the surgical site. The endoscope and the other instruments are positioned in the body of being through small openings, called portals. The surgeon views the surgical site through the endoscope to determine how to manipulate the other surgical instruments in order to perform the desired surgical procedure. In an endoscopic procedure only the relatively small portals are formed in the body. Therefore, such a procedure is often referred to as minimally invasive surgery. This is unlike a conventional surgical procedure in which a relatively large incision is often made in order to gain access to the surgical site. One advantage of performing endoscopic surgery is that since the portions of the body that are cut are reduced, the portions of the body that need to heal after the surgery are likewise reduced. Still another advantage of endoscopic surgery is that it exposes less of the interior tissue of the body to the open environment. This minimal opening of the body lessens the extent to which its internal tissue and organs are open to infection.
The ability to perform endoscopic surgery has been made possible, in part, by the availability of surgical instruments especially designed to perform this type of surgery. An endoscopic surgical instrument typically has an elongated body. One end of the body, often referred to as the distal end, is designed to be positioned at the surgical site. The opposed end of the body, referred to as the proximal end, extends out of the body. The distal end of the body is provided with some type of working head designed to manipulate the tissue against which it is placed. The proximal end of the body is provided with a mechanism for controlling the working head.
Some endoscopic surgical instruments are designed for use with motorized handpieces. Often, these instruments are called xe2x80x9ccutting accessoriesxe2x80x9d. These accessories typically include an elongated tube that forms the body of the accessory. The proximal end of the tube is provided with a hub used to releasably couple the tube to the motor rotor integral with the handpiece so that the tube rotates with the actuation of the motor. One type of cutting accessory is the bur. This accessory has a solid head; it is designed to selectively shape tissue, typically bone, against which it is placed. Other cutting accessories have drill heads that are used to bore into bone. Another type of endoscopic cutting accessory is the shaver. The shaver has a head with cutting edges. The shaver is used to selectively remove soft tissue from a surgical site. Many cutting accessories, in addition to having first, inner tubes that transmit rotational power, have second, outer tubes. The outer tube extends around the inner tube and is releasably held in a static position to the complementary handpiece. The outer tube serves as a shield that prevents tissue adjacent the cutting accessory from becoming entrained around the rotating inner tube. Moreover, the distal end of the outer tube that forms part of a shaver often has its own cutting edge. The moving cutting edge of the rotating inner tube and the static cutting edge of the outer tube form a scissors-like assembly that cooperate to cut the tissue against which the distal end of the shaver is pressed.
In order for it to be possible to perform endoscopic surgery, it is often necessary to supply irrigating fluid to and remove fluid from the surgical site. The simultaneous introduction of fluid to and removal of the fluid flushes debris, such as the severed tissue, away from the site. This enables the surgeon to have a clear view of the site. The introduction of the fluid also serves to expand, distend, the tissue in the vicinity of the site. This separation of tissue clears the field of view at the surgical site. Many powered handpieces and their complementary cutting accessories are provided with conduits designed to facilitate the introduction of fluid to and suction of fluid and debris from the surgical site. Specifically, often the inner and outer tubes of a cutting accessory are collectively dimensioned so that there is a small annular gap between the two tubes. This gap serves as the channel through which irrigation fluid is flowed through the outer tube and out the open distal end of this tube. The center of the inner tube typically serves as the suction conduit through which fluid and debris are drawn away from the surgical site. The distal end of this tube is provided with an opening. The hub at the end of this tube has an opening through which the tube is placed in fluid communication with a suction bore formed in the handpiece. A suction pump draws fluid and debris away from the surgical site through the distal end opening of the inner tube, the body of the inner tube, the tube hub, and the handpiece suction bore.
The development of elongated cutting accessories is one of the reasons why it has become possible to perform more surgical procedures endoscopically. To date, however, it has been difficult to provide relatively long endoscopic cutting accessories for powered surgical tools. This is because a cutting accessory is exposed to significant side loading forces when it is pressed against a surgical site in order to perform a surgical procedure. These forces flex the tubes forming the accessory. If the flexing is significant, the middle section of the inner tube may start to rub against an adjacent surface of the outer tube. This contact becomes a braking action, which can significantly slow or stop the rotation of the inner tube. The extent of the contact between these surfaces increases with the lengths of the accessory""s tubes. In particular, the problems associated with side loading can start to affect the performance of the cutting accessory once the length of the cutting accessory exceeds 7.8 inches.
Some solutions have been proposed to minimize the extent of the bending problems associated with long-length cutting accessories. These solutions include increasing the wall thickness of the material forming these tubes. One disadvantage of this solution is that the size of the irrigation and/or suction channels formed by these tubes decrease. If not enough fluid can be introduced into and/or removed from a surgical site through the cutting accessory, additional portals must be formed in body in order to serve as access ports for fluid flow paths. Also, increasing the thickness of the tube walls may make it necessary to increase the size of the portals that lead to the surgical site. Alternatively, one could possibly manufacture the tubes forming these cutting accessories out materials that are better able to be subjected to side loading without bending. However, taking this action can significantly increase the cost of providing these accessories.
Since many long-length endoscopic cutting accessories are not readily available, it has proven difficult to perform endoscopic surgical procedures at certain surgical sites that are significantly spaced from the outer surface of the body.
This invention relates generally to the structure of cutting accessories intended for use with powered surgical handpieces that are designed to perform endoscopic procedures. More specifically, this invention relates to the construction of cutting accessories that facilitates providing accessories that have a relatively long length.